Method of coating and remoistening gummed tapes



Sept. 3, 1957 H. L. HEISE. ET AL 2,805,172

METHOD OF COATING AND REMOISTENIEING GUMMED TAPES Filed Dec. 25, 1953 Prepare water solution of protein v animal glue and alkaline salt at an acid resin that is normally insoluble in water or acid media Coat the adhesive admixture on paper or other suitable backing Dry the coating Wind in roll s, slit or sheet, and convert into end product such as label or tape Reactivate cumming with moistening solution comprised of a water solution of acid or acid salt and formaldehyde or formaldehyde donor Apply label or tape while wet and tacky to surface of article to be labeled or taped Allow label or tape to dry thoroughly to attain maximum waterproof bond ATTORNEYS- United States Patent 9 METHOD OF CGATING AND REMOISTENHNG GUNIMED TAPES Howard L. Heise and Gordon McAllister, Troy, Ohio, as-

signors to The Gummed Products Compazzy, Troy, Ohio, a corporation of Ohio Application December 23, 1953, Serial No. 400,110

6 Claims. (Cl. 117-62) This invention relates broadly to water remoistenable gummed paper and tape. Specifically, it is concerned with gummings applied to label and tape structures from true colloidal solutions (as distinguished from dispersions and emulsions of discrete particles in an adhesive mixture) and which, upon activation by an insolubilizing solution, are designed to produce a water resistant quality in the glue line between said adhering structures and the surfaces to which they may be applied.

Gummings for this purpose have long been known and used. They have consisted chiefly of protein animal glue coated on paper and dried, or, as has been suggested in U. S. Patent No. 2,440,193, the protein glue may be admixed with a resinous emulsion or dispersion. As customarily used, such gummings are reactivated by a water solution containing formaldehyde or an aldehyde donor such as trioxane or glyoxal used either alone, or in combination with any of the well known and widely used protein tanning agents and assistants such as:

Aluminum chloride Aluminum sulphate Copper sulfate Ferric Nitrate Aluminum ammonium sulfate Chromic chloride Chromic nitrate Chrome alum The effect of these ingredients is to tan the protein glue and thereby render it insoluble in water. However, even a completely tanned and insoluble animal protein softens and tenderizes upon immersion in water. Where a resin emulsion or dispersion is used with the protein glue the chrome salt also acts to de-emulsify the resinous emulsion. The over-all action of such moistening solutions are, of course, two-fold. First, the water solution instantly activates the gumming to a plastic or more or less fluid condition as normally required in the application of any remoistenable gummed structure. Secondly, and simultaneously, the tanning and/ or denaturing agents in the water begin their insolubilizing action which continues progressively during the subsequent drying of the gumming-and for an indeterminate period thereafter. It is generally accepted, however, that no significant increase in tanning effect takes place after six weeks. The comparative degree to which the adhesive is rendered insoluble in usually measured 72 hours after application.

In following the practices of the heretofore known art, that is, by employing an animal glue film activated by formaldehyde or an aldehyde donor, it has been impossible to produce bonds possessing sufiicient water resistance to satisfactorily meet all the requirements for which this type of product should be applicable; Furthermore, while coatings made in accordance with the teachings of U. S. Patent No. 2,440,193 do generally improve the water resistant quality of the bonds produced therewith, a number of inadequacies have become apparent in commercial practice.

2,805,172 Patented Sept. 3, 1957 (1) In an admixture with animal glue, resinous emulsions, upon prolonged and continuous agitation as prevails in the industrial gumming application of adhesives to paper structures, often break completely or in part, and thus prematurely agglomerate with the result that the gumming then becomes grainy from the'precipitated resin emulsion, rendering the batch worthless or, if undetected, the product produced therewith. The use of larger amounts of emulsifying agent provides protection from this hazard but produces an'increased obstacle to deemulsifying the emulsion in its ultimate application in which it must be rendered water insoluble by the moistening solution, thus leading to the alternative inadequacy described below in (2).

(2) Coatings laid down from emulsified resins or developing from emulsified resins admixed with glue, after breaking of the emulsion, notoriously retain varying tendencies toward again re-emulsifying for the reason disclosed above, and other causes as well, unless various techniques of coalescing, annealing, etc. are employed, and which, in the ultimate tape application procedure are not practical.

Even various means of annealing, coalescing or otherwise completely denaturing such films that are known to have merit, have not proven adaptable to the class of product we are concerned with here.

(3) During manufacture of a gummed paper structure, the possible over-drying of a gumming formulated with a resinous emulsion may result in its coalescing or annealing prior to application in the end use for which it is intended. Such premature action tends to insolubilize the gumming with the result that it will not reactivate readily, thus, seriously reducing its ability to function as a remoistenable adhesive and to produce a strong wet tacky adhesive film, thereby critically impairing its applicating performance as well as weakening, if not nullifying the adhesive bond it is intended to produce.

(4) Because of the characteristics disclosed above, heretofore used combinations of gummings and tanning agents, are limited in practical use to the extent of the strength of the bond which they can potentially develop making it difficult and uncertain with presently used adhesives to comply in commercial practice, for example, with the requirements for water resistant gummed tape set forth in Federal Specification UU-T-l16b, Section 3.4.2. a

(5 As disclosed in U. S. Patent 2,440,193 the asphaltic emulsion is the more effective resinous emulsion additive from the standpoint of water resistance but its black color is not suitable for general label application.

(6) Dark-colored activating solutions, such as are derived from many chrome salts, discolor'label paper stock and, therefore, are not useful in bottle label application.

(7) Furthermore, and with reference to the foregoing, no combinations of glues and resin emulsion additives used as remoistenable gummings with tanning agents as activating and waterproofing solutions, have been used and/ or have provided a satisfactory water resistant bond for the application of pregummed, remoistenable labels to beverage bottles. A remoistenable gumming adhesive for this purpose must be capable, after its ultimate application to the bottle, of withstanding prolonged immersion in water, as may be practiced in a manner of chilling. It must be non-staining and easily removed by standard sanitary bottle washing methods without fouling the bottles, inside or out, or the washing equipment. In addition, when the bottle is grasped and pressure applied in a squeezing manner over the label, the water resistance must be of such order that the adhesive under the label will not slip in its contact with the glass and permit the bottle to pop from the grasp. a

Now, it is the purpose of our invention to provide a means of formulation that will eliminate the ditficulties resulting from the practice of the prior art and the product inadequacies thereof and to extend the usefulness of pregummed water remoistenable gurnmi-ngs into the field of waterproof label application for beverage bottles, etc.

The figure is a flow sheet of the process in accordance with our invention.

We have found that if the gumming used on the gummed sheet contains a water soluble alkaline salt of a normally water insoluble acid resin; and, if the activating solution used contains, in addition to a formaldehyde composition composed of formaldehyde or a formaldehyde donor such as glyoxal, an acid or an acid salt which-will react with the alkaline salt of the acid resin, that surprisingly, the strength of the water resistant bond thus produced is materially increased and its adherence to glass after prolonged immersion is devoid of any tendency toslip under application of pressure from any angle from a vertical-to a horizontal plane. Furthermore, we find that the associated difficulties of stability of the adhesive mix to mechanical agitation, as encountered in gumming processes, isexcellent. Stability to heat in the drying operation of manufacture is adequate, thus facilitating uniform production without danger or spoilage or variation of quality of product. The certainty of the reaction of the acid radical and the alkaline ion precludes the necessity of depending on the physical breaking of the emulsion to obtain a resinous additive of incomplete return to its unemulsified state. Thus, we have found adhesive combinations of our invention to produce up to 78% increase inwet adhesive water resistance and, likewise, that gummed tape produced therewith, shows similarly increased strength of the wet bond, tested in accordance with the requirements of Federal Specification UU-T-1l6b, Section 3.4.2.

In addition, we have produced in accordance with the disclosures of our invention gumming formulations for bottle labeling applications in which the label product has remained firmly adhered to glass after prolonged immersion in cold water and which cannot be removed without complete mutilation of said labels. At the same time, labels gummed with adhesives of our invention can be readily washed from the bottles in hot, normally alkaline washing solutions as commonly used in bottling plants, fouling neither the washing solution not the equipment nor the bottles inside or out.

To illustrate the results to be obtained when a protein gumming containing the alkaline salt of an acid resin, is activated with an aqueous moistening solution containing a formaldehyde donor and an acid salt tanning assistant, we have prepared the following 'series'of examples.

Example I is a conventional type of protein adhesive for this use. Examples II-VI are gummings to illustrate the principle of this invention and are admixtures of Staybelite Size with the glue mix used in Example I. Staybelite Size is the sodium salt of Staybelite Resin. Staybelite Resin is defined as follows? A hard, brittle, hydrogenated rosin. Color grade WG-WW; M. P. 168 F.; flash point, 398 F.; acid No. 162; sp. gr. 1.045 (20 0.); index of refraction 1.527 (20 C.); soluble in alcohol, ethyl acetate, acetone, aromatic and aliphatic hydrocarbons, and carbon tetrachloride; compatible With ethyl cellulose, Buna S proteins (such 'as casein and zein), rubber, vinyl resins, polystyrene and polyolefin resins (Vistanex), and waxes. Uses as a paraffin wax modifier; for pressure sensitive and heat sealing adhesive compositions; and for protective and decorative lacquers, printing inks and transparentizers'. Staybelite Size is a water soluble sodium (alkaline) salt of Staybelite Resin, a hydrogenated rosin."

Other alkaline salts may also be used. Instead of re- 4 peating the definition we will use the word Staybelite to indicate a type of resin as defined.

These were coated on 30"30-30 stock (two sheets of 30 lb. kraft paper laminated together by a 30 1b. layer of asphalt), all weights on the basis of 500 sheets 24" x 36". The coatings were made from a 50% total solids mix in water and oven-dried. The coat weight applied was 22 lbs.i3 lbs. same basis as above. The examples were prepared following the flow diagram of the figure.

Example I:

300 gram strength glue, 300 lbs.

100 gram strength glue, 1200 lbs.

Fish glue, 100 lbs.

Propylene glycol, 50 lbs. Example II: 90 parts of No. I, 10 parts Staybelite Size Example III: parts of No. I, 20 parts Staybelite Size Example IV: 70 partsof No.1, 30 parts Staybelite Size- Example V: 60 parts .of .No I, 40 parts Staybelite Size Example VI: 50 parts of No. I, 50 parts Staybelite Size To illustrate the effect obtained when 'gummings of this invention are activated with moistening agents of this invention, these above gummings were activated for application with two different moistening agents; A, a 4% solution of formaldehyde inwater, an example of heretofore used tanning moistening agents; and B, a solution of 2% aluminum chloride and 2% glyoxal in water. The latter is a moistening agent which has been previously used, but when used with gummings containing the sodium salt of an acid resin becomes illustrative of the effectiveness of the present invention. All samples were tested with both moistening solutions according to the method described in Federal Specification UU-T-l16b, Section 4.3.7.

The results obtained were as follows:

Moisteuing Solution, Wet Tensile Example No. Strength A, ounce B, ounce It is apparent that the results obtained with Examples II-V activated by moistening solution B were all higher than the results obtained with Example I (representative of what is currently in use) activatedwith either moistening solution, and that Examples 11 to VI all test higher when activated with solution B (which is representative of present invention moistening agents) than when activated with solution A.

To further illustrate the value of this invention, a sec- 0nd series of coatings'was made, :these were coated on 50 lb. (24x36-500 basis) sulfite bond paper with an English finish. This stock is commonly used as label paper for beverage bottles.

The adhesive coatings used were as follows:

Example VII was the samecoating mix as Example I Example VIII was the same coating mix as Example II Example IX was the same coating mix as ExampleIII Example X was the same coating mix as Example IV Example XI was the same coating mix-as Example V 4 Example XII was the same coating mix as Example VI These were activated by moistening With both moistening solutions A' and B, previously described, and applied to glass bottles and permitted'to age for 72 hours before testing by immersing in 80 F. water. These were examined 24 hours after immersion and the degree of adhesion was graded as follows:

1. Floated free v 2. Remained in place but would release if rotated vigorouslyinwater 1 3. Was not released by above but when pushed slid loose easily 4. Was not released by rotating in water, as in 2, and

when pushed tore at least 5% of label 5. Was not released by rotating and when pushed tore at least 15% of label 6. Was not released by rotating and when pushed tore at least 30% of label 7. Was not released by rotating and when pushed tore at least 50% of label 8. Was not released by rotating and when pushed tore at least 75% of label 9. Could not be released by rotating and when pushed all of the label tore.

Using the above grading, results obtained were:

It is apparent from the above that where a combination of a glue containing Staybelite Size was used with a moistening agent containing both formaldehyde donor and an acid salt that the wet adhesion to glass was much improved. In fact, the ratings of 6 or over indicate adequate adhesion, commercially acceptable for slipproof beverage bottle labeling.

Similar results are obtained if formaldehyde is used with aluminum chloride or with ferric nitrate, or if the formaldehyde donor is used with aluminum sulfate or copper sulfate. Commercially acceptable results are obtained, also, if the Staybelite Size is replaced by an alkali salt (preferably sodium) of common rosin or Petrax SS, which is a modified alkyd resin sold by the Hercules Powder Company or Belro Resin, also sold by the Hercules Powder Company, or by any water insoluble acid resin whose alkaline salts are water soluble.

It is apparent that it may be desirable in some applications to alter the ratio of formaldehyde or formaldehyde donor to the acid salt in the moistening solution, and that differences in the degree of waterproofing may also be obtained by varying the concentration of the ingredients in the moistening solution. Likewise, it is also known that different degrees of waterproofness will be obtained a by using glues greater or lesser of gram strength.

While various specific examples of compositions embodying the present invention have been described above, it should be understood that the examples cited and the particular proportions set forth are intended solely for illustrative purposes and that it is not intended to limit the scope of the invention except to the teachings herein disclosed.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is:

1. That improvement in the art of sealing which comprises formulating and applying to a sheet in a colloidal solution, a coating of a gumming composition consisting of a protein animal glue and a water soluble alkaline salt of an acid resin which is normally water insoluble in acid media, drying the coating on the sheet and subsequently activating the dried coating with an aqueous solution composed of a protein tanning aldehyde composition to which has been added an acidic material chosen from 6 a class consisting ofacids, and acid salts whichwill react with the alkaline salt of the acid resin, said'acidic material being added in a quantity sufficient to efiectively neutralize the alkaline salt which is rendering the resin soluble.

2. That improvement in the art of sealing whichcornprises formulating and applying to a sheet in a colloidal solution, a coating of a gumming composition consisting of a protein glue and a water soluble alkaline salt ofan acid resin which is normally insoluble in Water and acid media, drying the coating on the sheet and subsequently activating the dried coating with an aqueous.

solution composed of a protein tanning aldehyde composition containing an acidic material chosen from a class consisting of acids and acid salts reactive with the alkaline salt of the acid resin, said acidic material being added in such a quantity as to effectively neutralize the said alkaline salt to an extent sufficient to render it insoluble.

3. That improvement in the art of sealing which comprises formulating and applying to a sheet in a colloidal solution, a coating of a gumming composition consisting of a protein animal glue and a water soluble alkaline salt of an acid resin which is normally insoluble in water and acidic media, drying the coating on the sheet and subsequently activating the dried coating with an aqueous solution composed of a protein tanning aldehyde composition to which has been added a material chosen from a class consisting of acids and acid salts which will react with the alkaline salt of the acid resin, and which is present in an amount at least suiiicient to effectively neutralize the alkaline resin salt, the percentages of protein tanning aldehyde composition and acid salt being substantially equal.

4. That improvement in the art of sealing which cornprises formulating and applying to a sheet in a colloidal solution, a coating of a gumming composition consisting of a protein glue and a saponified hydrogenated rosin which is normally water insoluble in acidic media, drying the coating on the sheet and subsequently activating the dried coating with an aqueous solution composed of a protein tanning aldehyde composition containing a material chosen from a class consisting of acids and acid salts which are reactive with the saponified hydrogenated rosin, said material being added in such quantity as to effectively neutralize the saponified hydrogenated rosin, the percentages of aldehyde composition and material being substantially equal.

5. That improvement in the art of sealing which comprises formulating and applying to a sheet in a colloidal solution, a coating of a gumming composition consisting of a protein animal glue and a water soluble alkaline salt of an acid resin which is normally insoluble in water or acid media, drying the coating on the sheet and subsequently activating the dried coating with an aqueous solution composed of a protein tanning aldehyde composition to which has been added a material chosen from a class consisting of acids and acid salts which will react with the alkaline salt of the acid resin, said acid salt being of the class consisting of aluminum chloride and aluminum sulfate, ferric nitrate and copper sulfate, and added in such quantity as to effectively neutralize the alkaline salt.

6. That improvement in the art of sealing which comprises formulating and applying to a sheet from a colloidal solution, a coating of a gumming composition consisting of a protein glue and a saponified hydrogenated rosin which is normally insoluble in water or acidic media, drying the coating on the sheet and subsequently activating the dried coating with a material consisting of tanning solution composed of a formaldehyde composition containing a material reactive with the saponified hydrogenated rosin, said material being of that class of tanning agents and assistants consisting of aluminum chloride and aluminum sulfate, ferric nitrate and copper sulfate, said ,7 I material being added in such quantity as'to efiectively 1 j OTHER REFERENCES 7 mfutrafize the Said saponified hydmgwakd rosin Staybelite, Dreshfield, Ppr Trade Jeurnal," July References Cited in the file of this patn ti P g 4042- UNITED STATES PATENTS Chemlqal Trade Names and Commerclal Syn01 1yms,

Haynes, 1951, page 239.

2,440,193 Davis Apr. 20, 1948 FOREIGN PATENTS 351,732 Great Britain July 2, 1931 

1. THAT IMPROVEMENT IN THE ART OF SEALING WHICH COMPRISES FORMULATING AN APPLYING TO A SHEET IN A COLLOIDAL SOLUTION, A COATING OF A GUMMING COMPOSITION CONSISTING OF A PROTEIN ANIMAL GLUE AND A WATER SOLUBLE ALKALINE SALT OF AN ACID RESIN WHICH IS NORMALLY WATER INSOLUBLE IN ACID MEDIA, DRYING THE COATING ON THE SHEET AND SUBSEQUENTLY ACTIVATING THE DRIED COATING WITH AN AQUEOUS SOLUTION COMPOSED OF A PROTEIN TANNING ALDEHYDE COMPOSITION TO WHICH HAS BEEN ADDED AN ACIDIC MATERIAL CHOSEN FROM A CLASS CONSISTING OF ACIDS, AND ACIDS SALTS WHICH WILL REACT WITH THE ALKALINE SALT OF THE ACID RESIN, SAID ACIDIC MATERIAL BEING ADDED IN A QUANTITY SUFFICIENT TO EFFECTIVELY NEUTRALIZE THE ALKALINE SALT WHICH IS RENDERING THE RESIN SOLUBLE. 